The Flame Photometric Determination of Calcium, Magnesium and Sodium in Cast Iron

One of the most promising developments of recent years in the field of metallurgy has been the addition of very small amounts of alkali and alkaline earth salts to cast iron to give a nodular or spheroidal structure to the carbon present in the iron. Having several times greater strength than ordinary cast iron, with greatly increased ductility, this new metal offers many of the advantages of both cast iron and steel. Accurate determinations of alkalis and alkaline earths in this iron are necessary for control purposes, since a variable part of the elements added to the iron are lost during production. At the present time, spectrographic and gravimetric chemical analysis are the only accurate means available for the determination of small amounts of alkali and alkaline earth elements in metals. Both these methods possess certain disadvantages. Chemical methods for determining alkalis and alkaline earths are particularly time-consuming, and require meticulous handling by an experienced analyst. Inherent in spectrographic analysis are the errors due to the use of the photographic emulsion as a recording device. Alkali metal determinations on a spectrographic recording photographically in the usual ultraviolet region offer considerable difficulties where trace amounts are concerned. In recent years, flame photometric determinations of alkali and alkaline earth elements in various materials have been reported in the literature. The photometer appears to be the best method available for the determination of trace amounts of the alkali metals, and is also extremely sensitive to calcium and magnesium of the alkaline earth group. It offers many of the advantages of the direct reading spectrograph at a considerably lower cost to laboratories which do not have spectrographic facilities. Because of increasing interest in alkali and alkaline earth determinations in metals, the Allis-Chalmers Research Laboratories recently purched a Beckman Flame Photometer. The author was given the problem of developing a flame photometric method for determining small quantities of calcium, magnesium and sodium in cast iron to supplement existing spectrographic and chemical procedures. This thesis is an outgrowth of that research investigation